Calling subprocess gives error

Question

I had written following 2 programs,

# TempHello.py
def sayHello():
 print 'Hello World !'
sayHello()
# Subprocess.py
import subprocess
if __name__ == '__main__':
 print 'Calling other program'
 child = subprocess.Popen( "./TempHello.py" , shell=True)
 print subprocess.check_output()
 print 'Calling other program completed'

When I try to run the Subprocess.py program, it gives following error as,

 Calling other program
 ./TempHello.py: 2: ./TempHello.py: Syntax error: "(" unexpected
Traceback (most recent call last):
 File "/usr/mandar/AnuntaTech/eclipse_workspace/BackupManager/Subprocess.py", line 7, in <module>
 print subprocess.check_output()
 File "/usr/lib/python2.7/subprocess.py", line 537, in check_output
 process = Popen(stdout=PIPE, *popenargs, **kwargs)
TypeError: __init__() takes at least 2 arguments (2 given)

I am not able to figure out how to solve this problem. Please help.

• Some programmer dude: Is TempHello.py executable? Don't you need a hashbang as well?
• Mandy: Thanks a lot @JoachimPileborg, silly mistake from my side. Thanks a lot. Also calling subprocess.Popen('python ./TempHello.py') works equally for me.

Answer 1

Problem is that Popen is trying to execute TempHello.py as if it were a shell executable, when in fact it is a Python script. Simplest solution is fixing Subprocess.py like this:

import subprocess
if __name__ == '__main__':
 print 'Calling other program'
 child = subprocess.Popen( "python TempHello.py" , shell=True)
 print subprocess.check_output()
 print 'Calling other program completed'

In fact, you'll want to invoke Python executable and make it run your script.

On *nix platforms (thus, not including Windows), you can also use a shebang to specify which interpreter to use, like this:

#! /usr/bin/env python
def sayHello():
 print 'Hello World !'
sayHello()

Or

#! /usr/bin/python
def sayHello():
 print 'Hello World !'
sayHello()

and make the script executable with chmod u+x TempHello.py.

By the way, I suggest you to take a different approach in spawning Python scripts, if that's your purpose: have a look at multiprocess module.

Answer 2

You are running TempHello.py as a program. But it is just python source code. How about putting this line in the beginning:

#!/usr/bin/env python

and run

chmod u+x TempHello.py

before running Subprocess.py

• Stefano Sanfilippo: This solution requires a unix-like platform, it will not work on Windows and the like. Apparently, the OP is using Linux, but still he/she cannot consider this solution as being cross platform.
• HongboZhu: Thanks for your kind comments. But I guess the crux of the problem is pointed out and the question is solved in the simple answer.